1. Field of the Invention
This invention relates to multiscreen displaying apparatus and more particularly to a PJ unit cabinet structure and screen fitting structure in a multiscreen displaying apparatus made a wide screen by vertically and horizontally piling plural small size projecting units (also called cubic projecting displays mentioned as PJ units hereinafter) to provide a large picture apparatus for business.
2. Description of the Related Art
A large type video projector as a large picture displaying apparatus has been developed so that many people at once may see and hear a video. Three CRT picture images are provided corresponding to three primary colors of red, blue and green onto a large screen of about 40 to 60 inches and is of a front surface projecting type and back surface projecting type.
Nowadays, the performance of such large projecting type projector can be said to have considerably improved but is somewhat inferior to that of the CRT display in the picture brightness and the directivity. On the other hand, the CRT display has been popularized for the home television receiver but its 40 inch type is said to be the limit of the size.
Therefore, recently, in order to realize a large type screen over 60 inches, a system realizing a large picture as a whole by combining plural sets of small pictures has come to be used rather than one large picture. A multiscreen displaying apparatus made a wide screen by vertically and horizontally piling plural small size PJ units which are, for example, the above mentioned back surface projecting type projectors has come to be standard.
FIG. 24 shows a PJ unit alone of a conventional multiscreen displaying apparatus.
In FIG. 24, a cabinet of a PJ unit 30A consists of a barrel 31, a screen 33 and a screen fitting frame 32 for fitting the screen 33. An optical unit box (projector) consisting of a circuit part, projecting tube part and lens part not illustrated is contained inside the barrel 31. As clear from the same drawing, the total length of the cabinet of the PJ unit 30A combining the length of the barrel 31 with the length of the screen fitting frame 32 is determined by such distance at which a video of a size equal to the size of the screen 33 will be projected when the projected light from the above mentioned optical unit box (projector) 34 forms a focus normal in the optical design.
FIG. 25 shows a multiscreen displaying apparatus formed by vertically and horizontally piling conventional PJ units alone. Here, a multiscreen displaying apparatus formed of four PJ units 30A, 30B, 30C and 30D shall be explained as an example.
In FIG. 25, screens 33, 35, 36 and 37 arranged respectively on the front surfaces of the PJ units 30A, 30B, 30C and 30D are finished to be of structures so high in the rectangular precision as no slightest gap will be produced between the respective adjacent screens, that is, between the respective PJ units when the PJ units 30A to 30D are piled to be the multiscreen displaying apparatus.
Now, in said apparatus, as described above, the total length (equal to the sum of the length of the screen fitting frame 32 and the length of the barrel 31) is of the size equal to the normal dimension in the optical design, the unit of this long total length as it is must be transported, stored and assembled (that is, assembled into the multiscreen display) and, when it is necessary to rotate the cabinet in the installing operation particularly in a place narrow in the depth, the reduction in the operability will be remarkable.
The space from the optical unit box 34 to the screen 33 is merely hollow and is not effective except when a video is being projected. That is to say, it is necessary to transport a useless volume in the transportation and a wide (useless) storing space is required in the storing.
Further, as the optical unit box 34 and barrel 31 are of double structures in the rear of the cabinet, the weight of the materials by the double structures will be duplicated and the production cost will rise. Particularly, the influence of the weight will be large in case many plural PJ units are piled up to form a large picture, the slightest increase of the weight of each PJ unit of one set will have a very large influence on the total weight of the PJ units forming the large picture and will cause a grave influence on the load-resisting strength and handling ease of the cabinet, for example, when the units are piled up.
FIG. 26 is a cross-sectioned view on line A--A in FIG. 25.
As in FIG. 26, the cabinet of the PJ unit 30A is provided with a barrel 31, screen fitting frame 32, screen 33 and screen pressing metal fixture 38.
Said screen 33 consists of a Fresnel part 33B on the back surface side and a lenticular part 33A on the front surface side and is held by the screen fitting frame 32 and screen pressing metal fixture 38. This screen fitting frame 32 is formed to enclose the outer periphery of the screen 33.
The screen fitting frame 32 consists of a locking part 32A formed to be bent to the surface side of the screen 33 and a frame part 32B formed to enclose the outer periphery. The frame part 32B of this screen fitting frame 32 is fastened and secured to the barrel 31 with screws 39. By the way, this screw 39 is such flat head screw 39 that the screw head may come into the surface including the outer peripheral surface of the screen fitting frame 32 so that the adjacent PJ units (for example, 30A and 30B) may not hurt each other.
On the other hand, a screen pressing metal fixture 38 is provided on the screen back surface side so that the screen 33 may be inserted between this screen pressing metal fixture 38 and the locking part 32A of said screen fitting frame 32. This screen pressing metal fixture 38 is made of a plate-like member bent at one end to intersect substantially at right angles with the flat surface part including the end on the opposite side. The screen 33 is to be inserted between this bent part 38A and said locking part 32A. A hole a little larger than the screw diameter is made in this fitting screen pressing metal fixture 38 so that a screw 40 may come in through the hole. When the screw 40 is screwed from this hole into a screw hole provided in the screen fitting frame 32, this screen pressing metal fixture 38 will be fixed.
By the way, on the screen side surface of the screen fitting frame 32, a space part 41 is provided between the screen outer periphery and the screen fitting frame so that the screen 33 may be held by a proper tension. The other PJ units 30B to 30D are also of the same formation.
However, in such apparatus, after the plural PJ units 30A to 30D are piled up, in case such maintaining operation as replacing the screen is to be made, after all the other PJ units than the PJ unit in which the screen is to be replaced are removed, the operation will have to be made and thus there has been a very troublesome problem. This is because the flat head screw 39 used to fix the screen fitting frame 32 can not be removed with the multiscreen display assembled as it is. Therefore, there has been a problem that, in case the number of the piled PJ units increases, the troubles caused in the replacing operation will be unmeasurable.
Such material high in the optical characteristics as, for example, an acrylic material is used for the screen 33. On the other hand, from the viewpoint of the light weight and rigidity, an aluminum material is used for the screen fitting frame 32. Therefore, as the elongation and shrinkage due to the temperature and humidity will be different and in order to keep the screen 33 flat, the space part 41 will have to be provided between the screen fitting frame 32 and the screen 33 outer periphery. Therefore, since it is necessary for the locking part 32A to have a large width dimension, there have been problems that the boundary between the PJ units 30A to 30D will become large and the picture will become hard to see.